We're currently searching for a self hosted webinar software because we have customers that put a big focus on security and privacy, also we're located in Germany we have to fulfill German and European laws regarding privacy and security.

This is why we decided that US-hosted-only software is out of the picture, ideally we would want a solution to self host (open source or proprietary doesn't matter), costs also not that much of a concern but ideally we would want to buy a license one time without monthly or yearly costs.

We need the following functions:

moderated (moderators can create seminars and invite participants and also set default permissions and grant and revoke individual permissions, e. g. talking)

only web-browser needed (at least on the participant side)

no third-party applications required on participant side (Flash, Silverlight or worse own software etc.)

I hope I'm not using the wrong platform to ask this question. I searched the internet by myself but I'm basically looking for webinar users who would like to share their experiences.
Most services provide provider-hosted solutions only with fees per month/year or depending on group size. If there is no other solution this would do as well but only for providers located within the EU (bound by European law).